"I see you are kissing the baby on its forehead."
Translation:Je vois que vous embrassez le bébé sur le front.
The subject of the conjugated verb is "I/je"; "vous" is the direct object of the conjugated verb "see/vois". As a consequence, after "I see you/je vous vois", the next verb is in the present participle in English and in the infinitive in French.
If you develop the sentence, you get "I see you (while you are) kissing" and "je vous vois (alors que vous êtes en train d')embrasser."
Sorry for the mishap; I thought you were inquiring about a translation with an infinitive clause, which is also possible for this sentence.
"I see you kissing the baby" can also be understood as "I see that you are kissing the baby" and this construction is what you need in French: Je vois que vous embrassez le bébé. "Embrassez" is indeed conjugated since it has its own subject: "vous".
The rule related to the "second verb" applies when this second verb does not have a subject of its own, like "Je veux embrasser le bébé", or any construction with one of the verbs which can introduce another verb in the infinitive without a preposition.